Assigning priority to molecules on double/triple bonds?

[Chem_Mod]

Question: Can you explain how to assign priority when there's a double or triple bond? I'm looking at page 17, item #4. It says to simply expand the double/triple bonds to equivalent single bonds, but in the diagrams, I don't see why they added C's to the terminal N (first example), or to the terminal C (in the second example). Shouldn't they be H's?

[Chem_Mod]

Answer: The expansion should be consistent with the atoms it is bonded to before you do this exercise. Example 1: the Carbon next to (Csp2) is bonded to N so it is expanded with an N on either side of it. The N is always next to a C so it is expanded with C's around it. Example2: The terminal carbon is across from a carbon so it is expanded with C's on either side of it.

[Chem_Mod]

Q: Can you please explain the priority rules pertaining to double and triple bonds for the R,S system. The book says that the atoms of a double bond are replicated and that of a triple bond are triplicated. What does that mean?

[Chem_Mod]

A: It means make the same number and type of single bonds as there are double or triple bonds. So for c=c consider each c atom as having two c-c single bonds.